Voltage unit housing

ABSTRACT

A telecommunications protection unit includes a voltage unit having an electrically insulating base configured to house a diode module assembly and a voltage limiting cell therein. The voltage limiting cell and diode module assembly are retained within the housing by a bus clip. The housing includes structure for preventing damage to the voltage limiting cell and diode module assembly during placement of the bus clip thereon. The diode module assembly is a one-piece article including a bus bar and several diodes and terminals which can be used by itself or in a voltage unit to provide desired electrical effects and facilitate assembly of an electrical system such as a telecommunications protection unit. The terminals of the diode module are highly flexible to respond to excessive voltage and sneak current events encountered by telecommunications protection equipment, and the bus clip is constructed to provide a plurality of independently yieldable segments to accommodate diode stacks of variable heights and reduce manufacturing costs.

This application is related to co-pending U.S. application Ser. No.09/097,251 filed Jun. 12, 1998, entitled DIODE MODULE ASSEMBLY;co-pending U.S. application Ser. No. 09/096,689 filed Jun. 12, 1998entitled VOLTAGE UNIT HOUSING; and co-pending U.S. application Ser. No.09/097,315 filed Jun. 12, 1998, entitled FLEXIBLE VOLTAGE UNIT TERMINAL.

FIELD OF THE INVENTION

This invention relates to the protection of communication equipment, andmore particularly to improved arrangements for current and voltageoverload protection.

BACKGROUND OF THE INVENTION

Protecting telecommunications equipment in telephone central offices orother locations against voltage surges and sneak currents is well known.For example, U.S. Pat. No. 4,796,150 discloses a solid state protectorfor insertion in a telephone line having tip and ring conductors. Theprotector comprises a current unit, a voltage unit and a pair of springsassembled within a housing structure. The voltage unit includes solidstate devices that respond instantaneously to spurious voltage surges onthe telephone line in the tip conductor, the ring conductor, or both tipand ring conductors. When a voltage surge exceeds a predeterminedthreshold, the voltage device operates to ground the telephone linethereby insuring that the spurious voltage bypasses the telephoneequipment in the central office.

The voltage unit disclosed in U.S. Pat. No. 4,796,150 and similarvoltage units often include one or more metal clips for retaining thevarious diodes, terminals and voltage limiter of the voltage unit in adesired assembled state. Heretofore, however, such voltage units haveafforded no way to protect the delicate diodes contained therein as theclip is placed over the diodes. Consequently, the diodes oftenexperience chipping, crushing, and related damage at their edges duringplacement of the clip thereon. This situation often requires replacementof the damaged diode, thereby increasing the manufacturing costs andassembly time of the voltage unit.

SUMMARY OF THE INVENTION

The present invention provides a voltage unit for use in atelecommunications protection unit having an electrically insulatinghousing configured to house a diode module assembly and a voltagelimiting cell therein. The voltage limiting cell and the diode moduleassembly are retained within the housing by a bus clip.

To overcome the problem of diode damage that might otherwise occurduring placement of the bus clip, the voltage unit housing of thepresent invention includes structure for guiding the clip over the diodemodule assembly such that it avoids the diode edges and comes to restdirectly on oppositely directed faces of the diode module assembly andvoltage limiter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is an exploded, isometric view of an existing voltage unitadapted for use in a telecommunications protection unit;

FIG. 1B is a plan view of the assembled voltage unit of FIG. 1A;

FIG. 1C is a partially cut side view of the assembled voltage unit ofFIG. 1A;

FIG. 1D is a section view of the assembled voltage unit of FIG. 1A takenalong line D--D of FIG. 1

FIG. 2 is an exploded, isometric view of an embodiment of a voltage unitin accordance with the present invention;

FIG. 3 is an isometric view of the assembled voltage unit depicted inFIG. 2;

FIG. 4 is a sectional view of the assembled voltage unit depicted inFIG. 3;

FIG. 5 is an exploded, isometric view of an embodiment of a diode moduleassembly in accordance with the present invention;

FIG. 6 is an isometric view of the assembled diode module assemblydepicted in FIG. 5;

FIG. 7 is an electrical schematic diagram of the assembled diode moduleassembly depicted in FIG. 6;

FIG. 8 is an electrical schematic diagram of the assembled voltage unitdepicted in FIG. 3;

FIG. 9 is an exploded, isometric view of an embodiment of atelecommunications protection unit employing a voltage unit inaccordance with the present invention;

FIG. 10 is an isometric view of a further embodiment of an assembledvoltage unit in accordance resent invention;

FIG. 10B is a view of the voltage unit depicted in FIG. 10A fastened toa printed circuit board;

FIG. 11 is an isometric view of a further embodiment of an assembledvoltage unit in accordance with the present invention;

FIG. 12A is an isometric view of a preferred embodiment of a bus clipadapted for use with a voltage unit in accordance with the presentinvention;

FIG. 12B is an elevation view of the bus clip depicted in FIG. 12A;

FIG. 13 is an elevational cross-section view taken through a centralregion of a preferred embodiment of a voyage unit housing adapted foruse with a voltage unit in accordance with the present prevention; and

FIG. 14 is a plan view of a preferred embodiment of a contact adaptedfor use in a voltage unit in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Collectively referring to FIGS. 1A, 1B, 1C and 1D, there is shown avoltage unit manufactured by Lucent Technologies, Inc., adapted for usein a telecommunications protection unit. The voltage unit, identifiedgenerally by reference numeral 100, typically includes an electricallyinsulating base or housing 102 which may be formed from polybutyleneterephthalate (PBT) or other suitable moldable material. Voltage unit100 further currently includes a self-triggering surge suppressor (orsurgistor or voltage limiter) 104 constructed as a cell or disc package.Voltage limiter 104 is preferably a unidirectional type P247manufactured by Teccor Electronics. The voltage limiter 104 issandwiched between two metallic plates 106 having outwardly extendingelongate wing segments. Four diodes 108, two on either side of thevoltage limiter 104, are sandwiched between the elongate wing segmentsof plates 106. Diodes 108 are preferably PR4 type diodes manufactured byGeneral Instrument. A metallic terminal 110 (either a tip or a ringterminal) is disposed between each of the two sets of diodes 108 and oneof a pair of additional diodes 112, which are preferably of the same orsimilar type as diodes 108, is positioned exteriorly of a central regionof each of the metallic plates 106.

The operative electrical components of unit 100 are disposed withinhousing 102 in the manner most clearly depicted in FIGS. 1B, 1C and 1Dand are retained therein by a narrow (relative to the length of housing102) generally C-shaped metallic clip 114. Clip 114 electricallycontacts the diodes 112 and compressively maintains the unit 110 inassembled condition. Additionally, each of the terminals 110 of voltageunit 100 incorporates a notch 116 (FIG. 1B) generally in a mid-region ofeach of its side edges to engagingly retain the terminals within thehousing.

Although effective for its intended purpose, voltage unit 100 is costlyto manufacture and rather difficult to assemble. Specifically, all ofthe electrical components of unit 100 are discrete elements which arenot affixed to one another, yet must assume and maintain specificdispositions in the final assembly. If constant compressive force is notexerted against diodes 112 as clip 114 is placed thereon, or if clip 114is improperly positioned on the diodes 112, e.g., it pivots out ofproper placement alignment, the unit 100 may literally fall apart duringthe manufacturing process. Hence, as many as thirteen parts may have tobe recovered and realigned (both structurally and electrically) beforethe assembly may be reassembled. Further, because of their small sizeand delicate construction, one or more of the voltage limiters 104,metallic plates 106, paddle terminals 110 and/or diodes 108, 112 maybecome lost or damaged if the assembly process fails. Moreover, even ifassembly proceeds without apparent incident, the construction of housing102 is such that it affords limited protection of the diodes 112 fromcrushing, chipping or similar damage which may occur as a result of thecompressive and/or shear forces exerted by the clip 114 as it ispositioned on diodes 112. The clip 114 may also fail to retain theelectrical components within the housing if one or more of the diodes108, 112 becomes damaged and reduces its thickness during operation.

The voltage limiter 104, metallic plates 106, diodes 108, 112 andterminals 110 have utility separate and distinct from one another as asurge suppressor, simple conductor or diode, as the case may be.However, the cooperation of the several components to providesophisticated voltage surge protection is possible only if clip 114 ispresent. Moreover, their individual constructions do not render eitherthe diodes 108, 112, terminals 110 or clip 114 readily adaptable toother installation applications. For instance, unless considerablymodified, the various electrical components of voltage unit 100 areincapable of attachment to a printed circuit board or individual wireconductors.

A typical telecommunications protection unit for which voltage unit 100is adapted for use contains two heat coils for sneak current overloadprotection of the tip and ring circuits. One heat coil is in operativecontact with the tip terminal of the pair of terminals 110 as well as afirst office pin and a first line pin of the protection assembly. Theother heat coil is in operative contact with the ring terminal of thepair of terminals 110 as well as a second office pin and second line pinof the protection assembly. The term "office" and words of similarimport as used herein refer to components connected to the centraloffice telecommunications equipment (e.g., switching, transmissionequipment, telephone, modem or computer) whereas the term "line" and thelike refer to the outside telecommunications lines which transportsignals to and from the central office equipment.

Each of the terminals 110 make mechanical and electrical contact with arespective one of the heat coils. Either or both of the heat coils mustmove during a power surge or sneak current event. For the protectionunit to function properly, each terminal 110 must also move and maintainelectrical contact with its associated heat coil. Otherwise, protectionis lost and the damaging power is transmitted to the officetelecommunications equipment. The elongate wing segments of plates 106impart a yieldable spring force against diodes 108 which permits limitedmotion of the terminals 110 and diodes 108. To augment movement of theaffected terminal(s) 110 during a power surge or a sneak current event,the side of each of terminals 110 opposite the heat coils is in contactwith a compressed compression spring. The force exerted by thecompression springs against the terminals 110 is intended to assureconstant contact of either or both of terminals with the appropriateheat coil.

While generally useful to effectuate terminal movement under power surgeor sneak current events, voltage unit 100 may be susceptible to failurein the event of exposure to certain voltage surges or sneak currents.That is, the limited movement afforded to the terminals 110 may beinsufficient to provide rapid and reliable response to sudden movementsof the heat coil(s) which might cause momentary breaches in contactbetween the affected terminal(s) 110 and the heat coil(s).

Referring to FIG. 2, there is shown an exploded, isometric view of anembodiment of a voltage unit of the present invention, which findsbeneficial use, inter alia, in a telecommunications protection unit,generally referred to as 200. The voltage unit 200 includes anelectrically insulating base or housing 202. The housing is preferablymolded using a polybutylene terephthalate (PBT) or other suitablematerial.

Housing 202 includes a central region 202a bounded by a pair of endplates 202b, 202c and is configured with various receptacle areas andslots of suitable dimensions to house a diode module assembly 204 and avoltage limiter 206. The voltage limiter 206 is preferably a type IELlimiter manufactured by Texas Instruments. An electrically conductiveclip 208 described in greater detail with reference to FIGS. 12A and 12Bretains the diode module assembly 204 and the voltage limiter 206 withinthe housing 202 as shown in FIGS. 3 and 4. The material of the clip 208is preferably a beryllium copper alloy. When assembled, as depicted inFIG. 3, the voltage unit 200 establishes an electrical circuit asschematically depicted in FIG. 8 and results in a completed assemblyconsisting of four parts as opposed to the fourteen elements required toproduce the voltage unit disclosed in U.S. Pat. No. 4,796,150.

An exploded, isometric view of the diode module assembly 204 is depictedin FIG. 5. The diode module assembly 204 includes an electricallyconductive bus bar 502. The material of the bus bar is preferably acopper alloy. A first terminal 504, a second terminal 506 and a groundterminal 508 are each sandwiched between diodes 510 and 512. Eitherfirst terminal 504 or second terminal 506 may serve as a ring terminalwhile the other may serve as a tip terminal. For purpose of illustrationonly, terminal 504 may be considered a tip terminal and terminal 506 maybe considered a ring terminal. The diodes 510, 512 are preferably typePR4 diodes manufactured by Texas Instruments and the material of theterminals 504, 506 and 508 is preferably an annealed copper alloy. Thediodes 510 are each sandwiched between a respective terminal 504, 506and 508, and a terminal cap 514. The material of the terminal caps 514is preferably an annealed copper alloy. The bus bar 502, terminals 504,506 and 508, diodes 510 and 512 and terminal caps 514 are preferablysoldered or otherwise electrically and mechanically affixed together toform the unitary assembled diode module 204 as shown in FIG. 6. Whenassembled, the diode module establishes an electrical circuit asschematically depicted in FIG. 7.

Among the advantages arising from the integral or unitary constructionof the diode module assembly 204 of the present invention is that itsimplifies assembly of the voltage unit 200. For instance, the diodemodule assembly 204 is a single piece assemblage comprising severaldiode and conductor sub-components which can be easily and reliablyplaced as a unit in a correspondingly shaped receptacle in housing 202.By contrast, the various diodes, terminals and plates of the voltageunit 100 shown in FIGS. 1A-1D are "loose" items not integrally connectedto one another. If not carefully placed individually into specificpositions within housing 100, and maintained in those positions underthe influence of continuous compression until proper placement of clip114, one or more of these components may become misaligned or separatedfrom the others. Consequently, the proper arrangement of parts must becarefully maintained before assembly of the voltage unit 100 may becompleted. As will be appreciated, improper placement of any of theelectrical components of voltage unit 100 requires reassembly of theunit and raises manufacturing costs.

The peripheral dimensions of bus bar 502, terminals 504, 506 and 508 andterminal caps 514 of diode module assembly 204 are desirably greaterthan the peripheral dimensions of diodes 510, 512 with which they are incontact. With the diode module assembly 204 so constructed, the diodes510, 512 are effectively protected from physical trauma before, duringand after placement of the diode module assembly into housing 202.

Moreover, the modular nature of the diode module assembly 204 enables itto be manufactured and stored in inventory. Thereafter, it may be used,either by itself or as a component of a voltage unit (as will bedescribed in greater detail and in connection with the discussion ofFIGS. 10A, 10B and 11), in an in-line telecommunications protection unitand other applications to produce electrical circuitry functions farmore sophisticated, for example, than the individual diodes 108, 112 ofvoltage unit 100. Also, the diode module assembly 204 may be used withvoltage limiters other than voltage limiter 206 to achieve differinglevels of telecommunications equipment protection.

Referring to FIG. 9, there is shown an exploded, isometric view of atelecommunications equipment protection unit, generally designated 900,which employs a voltage unit 200 in accordance with the presentinvention. The protection unit 900 incorporates many of the structuralfeatures of the protection unit described in U.S. Pat. No. 4,796,150,the disclosure of which is incorporated herein by reference.

A presently preferred protection unit 900 includes a protector housing902 formed from any suitable non-conductive material which may be moldedand cured into a hollow, rugged and substantially rigid casing-typeconfiguration. Protection unit 900 further includes a voltage unit,preferably unit 200 described above, a right coil assembly 904, and aleft coil assembly 906. In a manner known in the art, each of the leftand right coil assemblies 904, 906 includes a housing formed fromsuitable nonconductive material which retains a central office pin 908communicable with the telecommunications equipment to be protected and aline pin 910 communicable with the outside telecommunications lineswhich transport signals to and from the central office equipment.Rearward projections of each of the line pins 910 are mechanicallysoldered and electrically connected to metallic, e.g., copper, sleeves912. Surrounding each of the sleeves 912 is a heat coil 914, one end ofwhich is secured to the sleeve and the other end of which is secured toa rearward projection of an appropriate central office pin 908. As isconventional, the heat coils 914 function as the sneak current limitersfor protection unit 900. The housings of each of the left and right coilassemblies 904, 906 are preferably provided with a groove 916 adapted toaccommodate approximately one-half of the circumference of a metallicground pin 918 of a grounding assembly 920. Grounding assembly 920further includes a metallic leaf-type ground spring 922 integrallyconnected to ground pin 918 and adapted for abutting contact with theground terminal 508 of voltage unit 200.

Protection unit 900 additionally includes a pair of metallic compressionsprings 924, only one of which is shown in FIG. 9. A first end of eachspring 924 contacts one of the tip and ring terminals 504, 506 ofvoltage unit 200 and a second end receives a metallic ball-like cap 926which normally abuts against the interior surface of a rear wall 928 ofhousing 902. Rear wall 928 further preferably comprises a pair ofopenings 930 only one of which is shown in FIG. 9. Each opening 930 isin alignment with a respective one of the caps 926 to permit testing forcontinuity of the line.

As known in the art, springs 924 exert compressive spring force againsttip and ring terminals 504, 506. Springs 924 are provided to maintaincontact between the tip and ring terminals and sleeves 912 duringperiods of normal operation and during voltage and/or current overloadevents. The operation of springs 924, which itself does not form a partof the present invention, is described more fully hereinafter.

FIGS. 10A and 10B reveal a further embodiment of a voltage unit inaccordance with the present invention. The voltage unit, identifiedgenerally by reference numeral 300, is constructed and functionssubstantially similarly to previously described voltage unit 200.Accordingly, only those elements of voltage unit 300 which materiallydiffer from voltage unit 200 or are otherwise necessary for a properunderstanding of the invention will be described in detail herein.

One difference between voltage unit 300 and voltage unit 200 lies in theconstruction of their terminals. For example, the tip and ring terminals504, 506 of voltage unit 200 lie in a common plane throughout theirlengths (FIGS. 2-6). Ground terminal 508, however, lies in part in theplane established by tip and ring terminals 504, 506 and in partdeviates from that plane. Indeed, at its distal end, ground terminal 508curves away from the common plane of tip and ring terminals 504, 506 toan extent that it extends substantially perpendicular to such plane. Itis this distal end of ground terminal 508 which abuts the ground spring922 (FIG. 9) when the protection unit 900 is in assembled condition.

In contrast, the three terminals of voltage unit 300, respectivelyidentified by reference numerals 304, 306 and 308, lie substantially ina common plane through their lengths. So constructed, terminals 304,306, 308 may be inserted into appropriately sized and spaced slots orholes provided in a suitable substrate 310 such as a printed circuitboard or the like and fixedly connected thereto by solder joints 312 orsimilar fastening means. It will also be understood that, although notillustrated, a diode module assembly similar to the diode moduleassembly 204 described hereinabove may also be affixed to a printedcircuit board or similar substrate if provided with terminalsconstructed substantially similarly to terminals 304, 306, 308 ofvoltage unit 300.

Referring to FIG. 11, there is shown a further embodiment of voltageunit according to the present, identified generally by reference numeral400. Like voltage unit 300 discussed immediately hereinabove, voltageunit 400 is substantially similar to voltage unit 200 and only materialdifferences therebetween will be emphasized herein. Additionally, likevoltage unit 300, a difference between voltage unit 400 and voltage unit200 is in the construction of their terminals. More specifically, theterminals 404, 406 and 408 of voltage unit 400 lie substantially in acommon plane throughout their lengths and are bifurcated at their distalends to form slots 410. Slots 410 are desirably of suitable width toreceive individual insulated wire conductors, one of which isrepresented by reference numeral 412, and sever the insulation of suchconductors so as to establish an insulation displacement connection(IDC) with such wires. And, although not illustrated, it will beappreciated that a diode module assembly similar to diode moduleassembly 204 may be affixed to wire conductors if provided withterminals constructed substantially similarly to terminals 404, 406, 408of voltage unit 400.

It will be understood that other diode module assemblies and/or voltageunit constructions consistent with the spirit of the present inventionmay be envisioned by those of ordinary skill in the subject art. Forinstance, the terminals of any of the diode module assemblies and/orvoltage units of the present invention may be modified so as toaccommodate wire wrapping or fitted with any suitable male or femaleconnection elements so as to permit their connection to virtually anypresently available circuitry, terminals or conductors.

FIGS. 12A and 12B respectively depict enlarged isometric and front viewsof a presently preferred embodiment of a bus clip 208 suitable for usein assembling any of the voltage units herein described. Clip 208 issubstantially C-shaped in cross-section and has a length L spanning amajority or, more preferably, substantially the entire length of housing202 between end plates 202b, 202c (FIG. 2). A benefit arising from busclip 208 extending for most and preferably nearly the entire distancebetween end plates 202b, 202c is that it is difficult to misalign theclip during placement. That is, end plates 202b, 202c function aslateral guides which effectively prevent undesirable rotation of the busclip 208 about axis A (FIG. 12A) during placement into housing 202.

Clip 208 may be formed from any suitable metal stamping and/or bendingtechniques to produce a substantially stiff yet slightly yieldablemember having flange portions 210, 212 joined by a web portion 214.Flange portions 210, 212 preferably include contiguous longitudinalinward and outward bends which together define opposed inwardlyprotruding elongate contact ridges 216 and 218. Upon assembly of voltageunit 200, for example, contact ridges 216, 218 compressively contact theouter surfaces of the voltage limiter 206 and diode module assembly 204,respectively, to retain and electrically connect the several electricalcomponents within the housing 202.

A pair of spaced-apart, substantially parallel slots 220 extendgenerally transverse to the length L of clip 208 and preferably divide asubstantial portion of web portion 214 and all of flange portion 212into three independently yieldable segments 222a, 222b ad 222c. Thecontact ridge 218 of segment 222a is adapted to contact the diode stack,specifically, the terminal cap 514, associated with terminal 506 (FIGS.5 and 6). Similarly, the contact ridge 218 of segment 222b is adapted tocontact the diode stack (specifically, the terminal cap 514) associatedwith terminal 508, and the contact ridge 218 of segment 222c is adaptedto contact the diode stack (specifically, the terminal cap 514)associated with terminal 504.

An advantage to segmentation of the bus clip 208 is that each segment222a, 222b, 222c may operate independently to produce an essentiallyuniform contact force on each stack of diodes and provide reliableretention of the voltage unit assembly. Hence, if one stack of diodesbecomes damaged and its thickness is reduced, the appropriateindependently yieldable segment 222a, 222b, 222c moves accordingly toensure contact with the damaged diode stack. Moreover, since eachsegment 222a, 222b, 222c independently moves to accommodate the heightof its corresponding diode stack, precise manufacturing tolerances arenot required for either the diode stacks or the bus clip 208 whichreduces manufacturing costs and simplifies assembly of the voltage unit.

As mentioned previously, housing 202 of voltage unit 200 is formed withvarious receptacle and slot areas to accommodate the diode moduleassembly 204 and voltage limiter 206. One of those areas, identified byreference numeral 224 is shown in FIG. 13. Area 224 is of sufficientsize to receive both the diode module assembly 204 and voltage limiter206 in the manner shown in FIG. 4. In existing voltage unit designs suchas, for example, voltage unit 100 (FIGS. 1A-1D), the exposed edges ofdiodes 112 may experience crushing, chipping and related damage as aresult of the compressive and/or shear forces exerted by the clip 114during assembly of the voltage unit. Such trauma may require replacementof one or more of the diodes thereby increasing manufacturing time andcost.

Housing 202 is desirably constructed to overcome this problem. Moreparticularly, housing 202 is desirably configured with structure forpreventing direct contact of the contact ridges 216, 218 of bus clip 208with anything other than the exposed oppositely facing surfaces of thevoltage limiter 206 and the diode stacks (specifically the terminal caps514 shown in FIGS. 5 and 6).

As seen in FIG. 13, a presently preferred structure for protecting thediode module assembly 204 and voltage limiter 206 from damage duringplacement of bus clip 208 is at least one, or more preferably, a pair ofguide members 226 and 228 provided along first and second opposite edgesof a longitudinal housing wall 230 connecting and extendingsubstantially perpendicular to end plates 202b, 202c. Guide members 226,228 each preferably include an outwardly inclined first portion 226a and228a, respectively. The first portions 226a, 228a urge outwardseparation of the contact ridges 216, 218 of the first and second flangeportions 210,212 of the bus clip 208 with respect to the housing 202 asthe clip is moved onto the housing (i.e., as the clip is moved fromright to left with respect to housing when the housing is disposed inthe orientation shown in FIG. 13). Adjacent and preferably contiguouswith outwardly inclined first portions 226a, 228a, guide members 226,228 further preferably include substantially uninclined second portions226b and 228b, respectively, for maintaining the first and second webs210, 212 in an outwardly urged or expanded condition and out of contactwith the exposed comers and outwardly facing surfaces of the voltagelimiter 206 and voltage diode assembly 204 as the bus continuesleftwardly with respect to the housing 202 in FIG. 13.

Optionally, guide members 226, 228 further comprise inwardly inclinedthird portions 226c and 228c, respectively. Third portions 226c, 228care disposed adjacent and preferably contiguous with the second portions226b, 228b and permit somewhat controlled inward movement or contractionof the first and second flange portions 210, 212 with respect to thehousing 202 as the bus clip continues leftward onto the housing. Uponpassing the guide members 226, 228 the contact ridges 216, 218 of busclip 208 come to rest directly upon the oppositely directed faces of thevoltage limiter 206 and the diode stacks, specifically, the terminalcaps 514, of the diode module assembly 204 as reflected in FIG. 4. Assuch, The fragile edges of the voltage limiter 206 and diode moduleassembly 204 are protected from harm from the bus clip 208 duringassembly.

FIG. 14 illustrates a presently preferred construction of the terminals504, 506, 508 described above in connection with FIGS. 5 and 6. Asmentioned previously, it is known to use compression springs intelecommunications protection units such as unit 900 (FIG. 9) to enhancecontact between the terminals of the voltage unit and the protectionunit's heat coil sleeves. Under the influence of an excessive powersurge or sneak current, the affected heat coil(s) heat up and the solderwhich connects a particular heat coil to its associated line pin melts.The sleeve about which the heat coil is wrapped is then urged to slidetoward under the influence of the compression spring and contact thegrounding assembly, thereby diverting the damaging voltage and/orcurrent to ground.

As the sleeve slides, it carries its associated heat coil. If the tipand/or ring terminal of the voltage unit loses contact with the movingsleeve, the damaging power is sent to the telecommunications equipmentrather than to ground. The paddle or terminal portions of contacts 110(FIGS. 1A and 1B), for example, are designed for limited movement underthe influence of a compression spring such as spring 924 (FIG. 9) uponthe occurrence of a voltage surge or sneak current event. However, somesudden movements of sleeves 912 may be of sufficient magnitude to breachcontact of the terminals 110 with the sleeves 912.

Terminal movement responsiveness may be enhanced by substituting thecompression springs 924 with heavier duty springs with higher springforce. However, the force associated with such springs may damage othercomponents of protection unit 900. Rather than using more forcefulsprings, the present invention proposes increasing the flexibility ofthe tip and ring terminals 504, 506.

Tip and ring terminals 504, 506 are preferably formed from copper alloyapproximately 0.016 inch in thickness. As illustrated in FIG. 14, eachterminal 504, 506 is preferably comprised of three portions. The firstportion 504a, 506a is disposed between diodes 510 and 512 (FIG. 6). Thesecond portion 504b, 506b is generally paddle-shaped and contacts theend of the compression spring 924 and the sleeve 912 as shown in FIG. 9.A comparatively narrow third portion 504c, 506c connects the first andsecond portions.

When the width W₃ of the terminal third portion 504c, 506c is about 50%or less of the width W₂ of the second portion 504b, 506b, increases interminal flexibility are realized versus terminals configured accordingto terminals 110 of voltage unit 100. Moreover, the considerableflexibility imparted to terminals 504, 506 by third portions 504c, 506creduces potential stresses from harming the integrity of the diode stackassemblies.

According to a presently preferred embodiment, for example, the width W₂of second portion 504b, 506b is preferably about 0.14 inches and thewidth W₃ of the third portion 504c, 506c is approximately 0.04 inches.W₃ is thus approximately 29% of W₂.

In contrast, the width of the corresponding notched portion of terminals110 of voltage unit 100 is approximately two-thirds of the width of thepaddle-shaped contact portion. Such a reduction in the terminal width ofterminals 504, 506, however, has been found to afford sufficientstrength to withstand the rigors normally encountered in the operationof a telecommunications protection unit yet provide terminal flexibilitysufficient to respond to sudden movements of sleeve 912 (FIG. 9).

We claim:
 1. A voltage unit including a diode module assemblycomprising:a central region and a pair of end plates at opposite ends ofsaid central region; a wall connecting said end plates, said wallincluding at least one outwardly inclined first portion, at least onesubstantially uninclined second portion adjacent said first portion, andat least one inwardly inclined third portion adjacent said secondportion, said first portion being adapted to urge a flange portion ofsaid clip outwardly with respect to said housing during placement ofsaid clip onto said housing, said second portion being adapted tomaintain said flange portion of said clip in an outwardly urgeddisposition with respect to said housing during placement of said cliponto said housing, and said third portion being adapted to permit inwardmovement of said flange portion of said clip with respect to saidhousing during placement of said clip onto said housing, wherein the atleast one outwardly inclined first portion is inclined at a firstinclination with respect to said uninclined second portion, and the atleast one inwardly inclined third portion is inclined at a secondinclination with respect to said uninclined second portion such that thefirst inclination is different than the second inclination.
 2. Atelecommunications protection unit including a voltage unit having adiode module assembly comprising:a central region and a pair of endplates at opposite ends of said central region; a wall connecting saidend plates, said wall including at least one outwardly inclined firstportion, at least one substantially uninclined second portion adjacentsaid first portion, and at least one inwardly inclined third portionadjacent said second portion, said first portion being adapted to urge aflange portion of said clip outwardly with respect to said housingduring placement of said clip onto said housing, said second portionbeing adapted to maintain said flange portion of said clip in anoutwardly urged disposition with respect to said housing duringplacement of said clip onto said housing, and said third portion beingadapted to permit inward movement of said flange portion of said clipwith respect to said housing during placement of said clip onto saidhousing, wherein the at least one outwardly inclined first portion isinclined at a first inclination with respect to said uninclined secondportion, and the at least one inwardly inclined third portion isinclined at a second inclination with respect to said uninclined secondportion such that the first inclination is different than the secondinclination.
 3. A housing for a voltage unit, said housing being adaptedto receive a clip having opposed flange portions connected by a webportion, said housing comprising:a central region and a pair of endplates at opposite ends of said central region; a wall connecting saidend plates, said wall including at least one outwardly inclined firstportion, at least one substantially uninclined second portion adjacentsaid first portion, and at least one inwardly inclined third portionadjacent said second portion, said first portion being adapted to urge aflange portion of said clip outwardly with respect to said housingduring placement of said clip onto said housing, said second portionbeing adapted to maintain said flange portion of said clip in anoutwardly urged disposition with respect to said housing duringplacement of said clip onto said housing, and said third portion beingadapted to permit inward movement of said flange portion of said clipwith respect to said housing during placement of said clip onto saidhousing, wherein the at least one outwardly inclined first portion isinclined at a first inclination with respect to said uninclined secondportion, and the at least one inwardly inclined third portion isinclined at a second inclination with respect to said uninclined secondportion such that the first inclination is different than the secondinclination.
 4. The housing as defined in claim 1 wherein said wallincludes a pair of said adjacent first and second portions, wherein oneof said pair is disposed on a first edge of said wall and the other ofsaid pair is disposed on a second edge of said wall opposite said firstedge.
 5. The housing as defined in claim 1 wherein said wall includes apair of said adjacent first, second and third portions, wherein one ofsaid pair is disposed on a first edge of said wall and the other of saidpair is disposed on a second edge of said wall opposite said first edge.